Manufacture of cast iron



Patented Nov. 9, 1943 2,333,141 monomer or, cssr mom I David B. Beeder, Evanston, lib, assignor to Electro Metallurgical Company, a corporation of No 1mm. Application September 29, 1942, Serial No. 460.125

5 Claims. (oi. 75-130) The invention relates to the manufacture of .1 m 1101!.

Manganese, usually in the form of ferromariganese, is often added to molten iron during the manufacture of various types of cast irons, to

produce divers beneficial effects. One of the important functions of manganese is to combine with any sulfur present in the iron and to inhibit to a large extent the adverse eflects which sulfur otherwise would produce. Another reason for adding manganese to cast iron is because of its and general scavenging actions, which have a beneficial eifect on the iron. Manganese is also added to malleable iron compositions for its retarding effect on the conversion of combined carbon to temper carbon during the malleabilizing anneal, when it is desired to produce so-called pearliticmalleable' iron. Dependin: on various factors, from about 0.2% to about 2% of manganese may be added to cast irons for these purposes.

It has been observed that irons to which fairly largeadditions'of manganese have been made sometimes exhibit what is known as pinhole porosity, a condition in which minute, sometimes microscopic, subcutaneous voids or pinholes" appear in the iron. These pinholes are quite dlflerent from the ordinary voids and imperfections causeddby improper casting procedure. There is some evidence to support the hypothesis that they are caused by gases in the iron. Whatever their cause, they are objectionis achieved by adding to the iron, preferably concurrently with the manganese, a readily re-.

ducibie metallic oxide such as iron oxide, nickel oxide, manganese oxide or chromium omde. The

that has been partially oxidized, for example by exposure to high temperatures in an oxidizing atmosphere.

The beneficial effects obtained by the invention have been demonstrated by tests conducted under commercial conditions. They are obtainable both in the production of pearlitic malleable iron and in other cast irons. Although the in.-

. vention has been described with particular referilarly, the invention is not limited to the treatment of pearlitic malleable iron but is also effective' in the treatment of cast irons in general.

I claim;

1. A method of treating a moltencast iron which method comprises adding to said molten iron about 0.2% to 2% manganese and metal oxide in an amount equal to about 0.25%" to of the manganese addition, the oxide addition inhibiting the form pinholes in such iron.

2. A method of treating .a molten castiron which method comprises adding to said molten iron about 0.2% to 2% manganese and iron oxide in an amount equal to about 0.25% to 10% of the manganese addition, the oxide addition inhibiting the tendency of the manganese to form pinholes in such iron.

3. In the method of producing pearlitic malleable iron which comprises adding manganese to a molten iron, the' improvement which com-' oxide equal to about 0.25% to 10% of the amount most generally suitable oxide for the practice of the invention is iron oxide, and convenient .sources'ofironoxideareironoresandmill-scaletweenabontone-quarterofonepercentandten per cent of the quantity of manganese added .andotherfactorabutingeneralitwill'bebe" totheiron'. 'lhisamoimtfurnishess'uillcient m n to inhibit the formation of pinholes without interfering with the effeptssought bythe addition. 'lhcb'eneiitsof-thoinvestionmayalsobe attaincdbyconcurrentb manganesean adding mthroughtheus ofaf of manganese added, to inhibit the formation of pinhole porosity in said iron.

4. In the method .of.producing pearlitic ma1-' leable iron which comprises adding manganese to a molten iron, the improvement which comprisesadding to said iron in conjunction with said manganese addition. fa quantity of iron oxide equal to about 0.25% to 10% of the amount of manganese added. to inhibit the formation of pinhole poroslty'in said iron. 7

5. In amethod of treating a molten cast iron which method comprises adding to such-iron a minor but substantial amount of manganese to produce desired metallurgical eflects, the said addition of manganese also tending to promote the formation of undesirable pinholes in such iron, the improvement which comprises adding .to such iron in admixture with the manganese manganese. A

, 1 :nsvm 13.3mm.

tendency of the manganese .to 

